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						<h1 itemprop="headline">Talk - Thomas Fernholz: Radio-frequency dressed detection of atomic clock states</h1>
						
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														Tuesday 13  December 2016,
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									<h2>Radio-frequency dressed detection of atomic clock states</h2>
<h3> Thomas Fernholz</h3>
<p>Our group currently investigates a new method to dispersively measure population and population difference of alkali atoms prepared in their two clock states (Fz=0). The Voigt effect, i.e.&nbsp;linear birefringence of the atomic medium, allows atom number detection via polarisation homodyning. To make&nbsp;full use of this common path interferometry and&nbsp;to&nbsp;achieve low technical noise levels, we perform sideband detection after adiabatically transforming the atomic states via radio-frequency dressing, see, e.g., (Lesanovsky2006). The balanced homodyne signal then oscillates at twice the dressing frequency, independent of&nbsp;field fluctuations, thus allowing for robust, phase-locked detection that circumvents low-frequency noise. Using probe pulses of two optical frequencies consecutively, we can detect atoms in&nbsp;both groundstate hyperfine manifolds separately and obtain population difference as well as total atom number in a single experimental cycle. Initial experiments with ensembles of 10^8&nbsp;rubidium-87 atoms allowed us to measure Rabi oscillations with a technical&nbsp;noise level of only 0.15 percent, currently limited by laser fluctuations. While this corresponds to a noise power of ~23dB above the atomic shot noise limit, single-laser two-colour operation should enable us to reach quantum noise limited performance, potentially allowing for the preparation of spin squeezed states via quantum non-demolition measurements (Hammerer2010). Our detection method can be used in atomic clocks and atom interferometric measurements.
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<p><br> Lesanovsky2006&nbsp;
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<p>I.&nbsp;Lesanovsky et al.,&nbsp;"Adiabatic radio-frequency potentials for the coherent manipulation of matter waves", Phys. Rev. A 73, 033619 (2006).<br> Hammerer2010
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<p>K.&nbsp;Hammerer, A.&nbsp;S.&nbsp;Sorensen and E.&nbsp;S.&nbsp;Polzik, "Quantum interface between light and atomic ensembles", Rev. Mod. Phys. 82, 1041 (2010).</p>
								
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